Effects of pulsed voltage rise rate on pulsed streamer discharge

Pulsed streamer discharge plasma, a type of non-thermal plasma, is known to generate various chemically active species and as such is applied to many fields such as water quality improvement and ozone generation. However, detailed physical properties of streamer discharge remain unclear. Therefore, basic research on pulsed streamer discharge is necessary. Previous studies have shown that voltage rise rates greatly influence streamer discharge, but few reports have focused on this. While peak voltage tends to vary under the influence of voltage rise rates, research to date has generally utilized an unfixed peak voltage. This study investigates discharge propagation phenomena at a fixed peak voltage under various voltage rise rates using an ICCD camera. In the experiment, a pulsed voltage with a duration of 100 ns was created using Blumlein lines and applied to a needle-hemisphere electrode. The applied peak voltage was about 71 kV with the electrode gap set at 24 mm as measured from the top of the needle to hemisphere surface. A decrease in the number of winding coils from 5 to 0 resulted in a pulsed voltage rise rate increased from 0.61 to 1.21 kV/ns. Important results are as follows. (1) The ending time of streamer head propagation was delayed, and the voltage at that time increased from 53.1 to 61.0 kV. (2) Streamer head velocity on average increased from 0.45 to 0.58 mm/ns. (3) Brightness value increase at the end of streamer head propagation. Our experimental results elucidate the relationship of pulsed voltage rise rate to various streamer discharge parameters. We conclude that pulsed voltage rise rate has a great influence on the physical characteristics of streamer discharge.